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With a queen and thousands of workers, ant colonies are often seen as a metaphor for human societies. Scientists have been studying their social behavior ever since 1882. Now, a recent study from Switzerland’s University of Lausanne gives groundbreaking insight into how these wee workers are able to organize.

“This work is beginning to reveal this whole sort of hidden network of communication,” said Iain Couzin, director of the Max Planck Institute for Ornithology. “We can really look at how [these] organisms come together and how they communicate to create this higher level society — a so-called superorganism.”

At issue is a process called trophallaxis, which is when ants exchange a social fluid (basically spit) containing nutrients and other substances. Scientists collected the spit, ran it through a mass spectrometer, and found a juvenile hormone never before seen outside of the ant’s bloodstream. They think it’s a signal that tells larvae to grow up, and that ants are using it to give their two cents on population control.

“Humans do [this] with voting and democracy. But here, we have each ant essentially deciding when they’re exchanging fluid,” said Adria LeBoeuf, an evolutionary biologist and part of the study. “Say I’m super opinionated and I think we need to make a ton more adults in this colony. I can put a ton of juvenile hormone like that in my fluid, but if I’m the only one who thinks like that, it gets defused.”

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In the summer, ants typically want larger workforces for foraging, while winter means scarce resources to pass around. The queen produces eggs all the time, so it’s up to the workers to decide how many adults join the colony. Unlike most insects, ants choose how long it takes to rear babies to adulthood, and larvae that get the juvenile hormone are twice as likely to survive (the others are eaten).

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“It’s probably a sort of crowdsourced decision,” LeBoeuf said.

Trophallaxis was previously thought as simply a way for ants to share food, but it’s much more than that — the spit contains immunity-related proteins that ants may be sharing to prevent each other from getting sick, for example, and it also contains hydrocarbons that signal their identity (ants will kill outsiders from different colonies, even if they’re part of the same species).

“Each individual is relatively simple, but, together, they can give a remarkable rise of intelligence,” Couzin said.

In other words, ants may not be seeing the bigger picture when they make decisions, but they’re definitely smarter than we think.


Kelly Kasulis is a journalist living in Boston and the deputy digital editor of The GroundTruth Project. Follow her on Twitter @KasulisK.